Osseointerfaced implanted artificial tooth

ABSTRACT

An artificial tooth implantable in a jaw bone utilizing a tooth root having distal and proximal end portions. The distal end portion of the root extends into the jaw bone and is fixed to the jaw bone. A hollow root extends from the proximal end portion of the root which is accessible from the outer surface of the jaw bone, toward the distal end portion of the root. A post has a first end portion which extends into the hollow of the root and is fixed to the root. A second portion of the post extends outwardly from the hollow and has an outer surface which slopes downwardly toward the first portion of the post. A crown is connected to the second portion of the post.

BACKGROUND OF THE INVENTION

The present invention relates to a novel osseointerfaced implantedartificial tooth which provides a permanent replacement for a naturaltooth. In the past, many systems have been proposed for the implantationof artificial teeth. For example, diverse designs with screws, nails,blades, and the like which are loaded immediately upon insertion in thejaw bone. These implants generally result in scar formation around theimplant with insufficient gingival seal, causing chronic infection, boneloss, and the eventual removal of the implant itself. For example, U.S.Pat. Nos. 2,857,670 and 3,579,831 describe these systems.

Later designs, such as that shown by U.S. Pat. No. 3,589,011, describe atwo stage implant where a shank, or hollow pin, is used as the root ofthe artificial tooth. A superstructure is then attached to the shank byutilizing the hollow herewithin to support the super structure,including the crown of the artificial tooth thereabove. U.S. Pat. Nos.3,797,113; 3,979,828; 4,178,686; 4,195,409; 4,259,072; 4,270,905; and4,324,550 describe this type of system. The root portion in many casesbecomes resorbable which eventually weakens the implant necessitatingremoval. Many materials such as polymethylmethacrylate eventually causetissue necrosis and scar formation.

U.S. Pat. Nos. 4,215,986 and 4,318,696 describe implants which addressthe problem of protecting destruction of the artificial tooth by themasticatory forces that overload. It has been found that adjacentnatural teeth have also been damaged by this type of implant, causingthe breakdown of tissue supporting the natural tooth. An artificialimplant system which overcomes the disadvantages of the prior arthereinabove described would be an extremely useful advance in the dentalfield.

SUMMARY OF THE INVENTION

In accordance with the present invention, a novel and usefulosseointerfaced implant system is described which may be permanentlyaffixed to the jaw bone is provided.

An artificial tooth of the present invention is implantable in the jawbone (alveolar) and employs an implantable tooth root. The tooth roothas a distal end portion extending into the jaw bone and a proximal endportion being accessible from the outer surface of the jaw bone. Theroot further includes a hollow extending from the proximal end portionof the root toward the distal end portion of the root. The root mayinclude means for tapping, or self tapping the same in relation to thejaw bone during placement. Means is also provided for fixing the root tothe jaw bone, such as a threaded surface. The hollow of the tooth rootprovides a place of fixation for the remainder of the artificial tooth.A post threads or otherwise fixes to the hollow of the tooth root andextends upwardly away from the jaw bone. The hollow may be sealed duringa healing period to further strengthen the tooth root, and to maintainan unobstructed place of fixation for the post. The post may have afirst portion fitting within the hollow of the root and a second portionextending outwardly from the hollow. The post second portion may alsoembrace an outer surface which slopes downwardly toward the firstportion of the post, and inwardly toward the center of the post. This socalled obtuse angle provides a tight contact between the gingiva and theimplant and protects this contact as well.

A crown is then connected to the post, specifically the second portionof the post extending outwardly from the hollow of the tooth root. Thesecond portion of the post may also be formed such that a base connectsto the first portion of the post and a stem extends from the base of thesecond portion of the post. Means may also be provided for breakablyconnecting the base to the stem of the second portion of the post. Inthis manner, excessive lateral forces would shear the post rather thantraumatizing the implant or the jaw bone itself.

To limit the elasticity of the upper structure, the second portion ofthe post may be coated with a polymer which would lie between the crownand the post. The polymer acts as a shock absorber and protects the boneagainst sudden high stress. Moreover, the polymer, or plastic coating,must have an elasticity which would limit mobility of the implantsystem; thus precluding damage to the bone around the natural teeth.

The base of the second portion of the post may include a dimension thatextends a greater distance transversely in relation to the root than atransverse dimension of the stem of the second portion of the post. Thusa platform is provided for the plastic or polymer coating against shearstresses thereupon.

Another embodiment of the present invention utilizes a spacer and splineas the post. Means for fixing the spacer adjacent to spline and betweenthe root and crown is also provided. The spacer may include the slopingouter surface of the post. Such a spacer would provide the dentalpractitioner with a method for adjusting the height of the same abovethe artificial tooth root. The spacer would also have means of turningthe same in relation to the spline. Thus, the spacer and post fittinglyengage one another.

The implant of the present invention may also include means forpermitting the attachment of a denture to the post and the plastic,metal or like coating there around.

It may be apparent that a novel and useful artificial tooth implantablein the jaw bone has been described. It is therefore an object of thepresent invention to provide an artificial tooth implantable in a jawbone which provides satisfactory service over a long term.

It is another object of the present invention to provide an artificialtooth implantable in a jaw bone which closely resembles the mobility ofthe natural tooth, thus permitting the patient to chew in a normalmanner and protect against parafunctional forces.

It is yet another object of the present invention to provide anartificial tooth implantable in a jaw bone which may be used insubstitution for a single tooth or a group of teeth as well as beingconnectable to natural teeth.

Still another object of the present invention is to provide anartificial tooth implantable in a jaw bone which protects against foodparticles being wedged between the gingiva and the implant during thechewing process, and against traumatizing of the contact site betweenthe gingiva and implant.

Yet another object of the present invention is to provide an artificialtooth implantable in a jaw bone which has a predetermined breakage pointof a portion thereof, upon the application of a predetermined shearforce, thus protecting the implant and/or the jaw bone itself.

Another object of the present invention is to provide an artificialtooth implantable in the jaw bone which utilizes a post having aremovable section which permits the dental practitioner to adjust theheight of the post in relation to the tooth root.

Another object of the present invention is to provide an artificialtooth implantable in the jaw which permits the dental practitioner toremove all portions of the implant, and replace the same with newportions, except the artificial root.

The invention possess other objects and advantages, especially asconcerns particular characteristics and features thereof which willbecome apparent as the specification continues.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an embodiment of the present inventionshowing a portion of the jaw and gum in broken away configuration.

FIG. 1A is a view taken along line 1A--1A of FIG. 1.

FIG. 1B is a view taken along line 1B--1B of FIG. 1.

FIG. 1C is a view taken along line 1C--1C of FIG. 1.

FIG. 2 is a sectional view of another embodiment of the presentinvention.

FIG. 3 is a sectional view of another embodiment of the presentinvention.

For a better understanding of the invention, reference is made to thefollowing detailed description of the preferred embodiment which shouldbe taken in conjunction with the hereinabove described drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various aspects of the present invention will evolve from the followingdetailed description which should be taken in conjunction with thehereinabove described drawing. The invention as a whole is shown in thefigures by reference character 10 and may include as one of its elementsan implantable tooth root 12.

Root 12 may be constructed of a relatively rigid biocompatable material.For example, titanium would be a satisfactory material under thiscriteria. Root 12 is roughly cylindrical in shape and possesses athreaded surface 14. Root 12 may also include a self tappingconstruction, FIG. 1 broken away portion, of known construction. Root 12includes a hollow portion 18 which extends from the upper surface 20 ofroot 12 toward the lower surface 22 thereof. Thus, proximal end portion24 of root 12 extends to the outer surface of jaw bone 26. Distal endportion 28 of root 12 extends into the jaw bone 26 as far as isnecessary for a satisfactory implantation. Threaded surface 14 of root12 threadingly engages the threaded surface of jaw bone, FIG. 1C, 26created by self tapping means 16. Thus, this threading engagement may beconsidered means 30 for fixing root 12 to jaw bone 26. Slot 32 permitsthe user to use a driving means to turn root 12 during the tapping ofjaw bone 26. It should be noted that a screw 34 is temporarily placed inhollow proportion 18 and is held in place by the threaded surface 36 ofscrew 34 engaging threaded surface 38 of root 12 within hollow portion18. Turning to FIG. 1A, it may be seen that screw 34 is temporarilyinserted into hollow 18 during first stage of the implant which will befurther described hereinafter.

Post 44 includes a first portion 46 which fits within hollow 18 of root12. A second portion 48 extends outwardly from hollow 18 and upwardlyfrom the surface of jaw bone 26. Second portion 48 includes an outersurface 50 which slopes downwardly toward first portion 46 of post 44and inwardly toward the center of post 44. This permits the tightfitting of gingiva 52 to the outer surface 50. The sloping surface 50also acts as a shelter against food particles wedging between surface 50and gingiva 52. It should be added that the prevention of food particlesfrom entering the space between the gingiva and the outer surface 50 ofthe post prevents damage to the implant and the living tissue thereat.Means 54 fixes first portion 46 of post 44 within hollow 18 of root 12.Such means may take the form of providing first portion 46 of post 44with a threaded surface 56 which engages threaded surface 38 of hollow18. It may be apparent that threaded surface 36 of screw 34 previouslyengaged the same threaded surface 38 of hollow 18, FIG. 1B. Post 44 mayagain be constructed of a fairly rigid material such as titanium. Secondportion 48 of post 44 may include a base 58 connected to first portion46 of post 44. Stem 60 extends from base 58 upwardly from jaw bone 26.As shown in the embodiment in FIG. 1, stem 60 is narrower transverselythan base 58. Means 62 breakably connects base 58 to stem 60. In otherwords, second portion 48 of post 44 includes a weakened undercut portion64 which surrounds the connection area between base 58 and stem 60.Thus, any excess lateral or shear forces will cause the breakage of stem60 in relation to base 58 and thereby protect root 12 in bone 26.Undercut portion 64 is filled with a glue 66 which also surrounds stem60. Glue 66 is used to attach a layer of resilient material 68 such assilicone, polysulphone, and the like. The thickness in quality ofresilient layer 68 may be predetermined to restrict the range ofmovement of the upper structure to about 200 microns. Resilient layer 68also acts as a shock absorber to protect the bone 26 against sudden highstress. Finally, a crown 70 may be formed as shown in FIG. 1.

Turning to FIG. 2, it may be seen that another embodiment of the presentinvention is provided. Post 44 includes a first portion 46 which fixesto root 12 in the same manner as the post shown in FIG. 1. However, theupper portion 48 has been split into a spline 72 and a washer, or spacer74. Means 76 fixes spacer 74 to spline 72. As shown in FIG. 2, means 76takes the form of a threaded outer surface 78 of spline 72 engaging athreaded surface 80 of spacer 74. Means 82 is provided for turningspacer 74 in relation to spline 72. Upper portion 84 of spline 72 mayagain break in relation to lower portion 86 thereof via means 62. Incertain cases, spacer 74 may be replaced with one having a differentheight to compensate for dimensional adjustments to root 12. Means 82 inthe form of openings 88 and 90 permit the use of tool to perform thisturning or rotational action.

Turning to FIG. 3, it may be seen that upper portion 84 of spline 72 maybe reduced in size and a new resilient layer having a groove 92 isplaced over upper portion 84. A denture 94 may be snapped into place bythe use of "O" ring 96. It should be noted that if any portion of spline72 or post 44 break by the use of means 62, remainder of post 44 orspline 72 within root 12 may be removed and replaced.

In operation the jaw bone 26 is made visible to the dental practitionerby the use of a surgical device. Root 12 is tapped into place usingtapping means 16 such that upper surface 20 of root 12 is accessible atthe outer surface of bone 26. The drills used to locate the root openingare cooled to protect the bone against burning during this process.Screw 34 is inserted into hollow 18 of root 12 and covered by gingiva 52for approximately four months. After this time period pilot hole 42permits the dental practitioner to locate screw 34 through the gingiva52 covering screw 34. A special cutting instrument removes the overlyingtissue to reveal screw 34. Screw 34 is then removed and post 44 orspline 72 and spacer 74 are inserted within hollow 18 of root 12. Itshould be apparent that the superstructure consisting of the crown andresilient layer 68 could be attached to post 44 or spline 72 and spacer74 after fixation of the post 44 or spline and spacer 72 and 74 to root12. Resilient layer 68 will separate under pressure, such as thepressure applied by a plier-like device. Separation of resilient layer68 from post 44 permits the dental practitioner to inspect, and/or alterthe superstructure of the implant system. Post 44 would also beremovable from root 12. As heretofore described, spacer 74 may bereplaced with a spacer of a different height. Upper portion 84 of spline72 may be cut down to provide for the insertion of a denture. Thus, allportions of the artificial tooth are replaceable, except the root 12.

While on the foregoing embodiments of the present invention have beenset forth in considerable detail for the purposes of making a completedisclosure of the invention, it may be apparent to those of skill in theart that numerous changes may be made in such detail without departingfrom the spirit and principles of the invention.

What is claimed is:
 1. An artificial tooth implantable in a jaw bonecomprising:a. an implantable tooth root, said root having a distal endportion intended for extending into the jaw bone and a proximal endportion being accessible from the outer surface of the jaw bone; saidroot further including a hollow extending from said proximal end portionof said root toward said distal end portion of said root; b. means forfixing said root to the jaw bone; c. a post, said post having a firstportion fitting within said hollow of said root and a second portionextending outwardly from said hollow; said second portion having anouter surface which slopes downwardly toward said first portion of saidpost said second portion of said post further including a base connectedto said first portion or said post; a stem extending from said base; anda weakened portion at said connection between said base and stem forbreakably connecting said base to said stem; d. means for fixing saidfirst portion of said post within said hollow of said root; e. a crownconnected to post.
 2. The artificial tooth of claim 1 in which saidweakened portion at said connection between said base and stem forbreakably connecting said base to said stem includes an undercut portionthereat.
 3. The artificial tooth of claim 2 which further comprises alayer of resilient material laminated between said crown and said post.4. The artificial tooth of claim 3 in which said second portion of saidpost, and said layer of resilient material further include means forholding a denture thereto.
 5. The artificial tooth of claim 2 in whichsaid base of said second portion of said post includes a dimension thatextends a greater distance transversly in relation to said root than atransverse dimension of said stem of said second portion of said post,said second portion outer surface sloping downwardly toward said postbeing defined to also slope inwardly toward the center of said post. 6.The artificial tooth of claim 1 which said post additionally comprises aspacer and means for fixing said spacer adjacent said post between saidroot and said crown, said spacer providing said sloping outer surface.7. The artificial tooth of claim 6 in which said spacer includes meansfor turning said spacer in relation to said post.
 8. The artificialtooth of claim 7 in which said root includes means for tapping said rootin relation to the jaw bone during placement of said root in the jawbone.